The present invention relates to a laminated electronic component; and, more particularly, to a laminated electronic component including a plurality of dielectric sheets laminated on top of another, each of the sheets having a conductive pattern, and through-holes, wherein each of the through-holes having an elongated shape along a lengthwise direction of the conductive pattern, and the conductive patterns are electrically connected through the through-holes.
A prior art laminated inductor is disclosed in FIGS. 9 and 10, wherein FIG. 9 offers an exploded perspective view of the laminated inductor and FIG. 10 gives a top planar view of a ferrite sheet incorporated therein.
The laminated inductor is provided with a laminated body of a substantially rectangular shape having therein internal electrodes forming a coil and a pair of external electrodes formed at both ends of the laminated body, respectively, the external electrodes being electrically connected to the internal electrode. The internal electrode forms the coil which is wound to allow a direction of a magnetic flux generated by the coil to be substantially identical to a direction in which the external electrodes are connected. Both ends of the coil are extracted out of the laminated body to be connected to the external electrodes, respectively.
The laminated body is made of magnetic material such as a ferrite. As shown in FIG. 9, the laminated body 101 is formed by pressing the plurality of the laminated ferrite sheets in a direction in which the external electrodes are connected. A conductive pattern 103 is formed on each of the ferrite sheets 102. The conductive patterns on the vertically adjacent sheets are electrically connected to one another through the through-hole 104. The conductive pattern is formed by applying a conductive paste on the ferrite sheet 102 having the through-hole 104. During the applying of the conductive paste, the conductive paste is charged through the through-hole 104. Accordingly, an electrical connection is achieved between the vertically adjacent ferrite sheets 102.
As shown in FIG. 10, the conductive pattern 103 has a substantially one end-opened rectangular shape at a center of each of the ferrite sheets, with one end thereof having a land 105 for an electrical connection with the through-hole 104. Further, the conductive pattern 103 is formed to have only the land 105 at both ends of the laminated body in order to extract the coil to a surface of the laminated body.
In such an inductor, it is important to guarantee a stable electrical connection between the conductive patterns through the through-hole. Especially, in the laminated inductor where the ferrite sheets are laminated and pressed in a direction in which the external electrodes are connected, it is difficult to guarantee the stable electrical connection, since the number of electrical connections through the through-hole is increased. Important cause of the unstable connection in the electrical connection through the through-hole may result from a misalign of the ferrite sheets therebetween. The misalign of one ferrite sheet from other ferrite sheet may further reduce a contact area between the conductive pattern and the through-hole, which causes the contact resistance to increase, thereby permitting a reduced amount of the current to be flown therethrough.
In order to solve such problem, the prior art laminated inductor 100 has the land 105 formed around a portion which is connected through the through-hole 104. A diameter of the land 105 is larger than a width of the conductive pattern serving as the coil; and is large enough to surround the through-hole 104. In this configuration, the electrical connection together with the necessary contact area between the land 105 and the through-hole 104 can be stably guaranteed, even if the ferrite sheets are misaligned with one another within an acceptable range.
In the prior art laminated inductor, however, the conductive pattern 103 does not have an ideal shape forming the coil due to the shape of the land 105; and a self resonant frequency(f0) is reduced due to an increase of a floating capacity between the land 105 and the external electrode.
It is, therefore, a primary object of the invention to provide a laminated electronic component wherein an stable electrical connection between electrodes can be guaranteed, maintaining its electrical properties.
The above and other objects of the invention are accomplished by providing a laminated electronic component having a plurality of insulating layers each of which is provided with a conductive patterns forming an internal electrode, said component comprising an elongated through-hole elongated along a length of the conductive pattern and connecting the conductive patterns on different insulating layers.
In the laminated inductor constructed in this manner, since the elongated through-hole is a hole elongated along a length of a branch of the coil conductive pattern, the electrical connection between the coil conductive patterns or between a coil conductive pattern and a lead conductive pattern can be maintained without necessitating a land for connecting to the normal through-hole. For this reason, increasing of a floating capacitance or reduction of a self-resonant frequency which may occur due to an existence of the land can be prevented. This configuration can cover more serious degrees of misalignment between the insulating layers, maintaining a sufficient contact area between the conductive patterns.
In accordance with another feature of the present invention, in the laminated electronic component, a lengthwise direction of the elongated through-hole is at a right angle with a direction of the conductive pattern formed on a directly lower insulating layer than that having the elongated through-hole. The present invention can accommodate a misalignment between the elongated through-hole and the insulating layers, maintaining a sufficient contact area therebetween.
In accordance with another feature of the present invention, in the laminated electronic component, the plurality of internal electrodes form a coil. Further, the laminated electronic component further comprises a pair of external electrodes being electrically connected to both ends of the coil, respectively, the external electrodes positioned parallel to a direction of a magnetic flux generated by the coil.